Argh... I'd posted quite a long answer but it's been eaten up by the Interwebs.
Anyways, nevermind, I've since found the description for the field:Progressivo di partecipazione, a partire dal valore 1. Da incrementare per eventuali acquisti successivi al primo nella stessa partita/sessione di gioco.

Does that help?

I thought partecipazione might mean amounts the player spends on the game, like "shares" or "contributions" - but I'm pretty sure it just means "participation", that's how it's been translated consistently through the document.